Enantioselective dearomative [3 + 2] annulation of 3-hydroxy chromanones with azonaphthalenes

Abstract

Enantioselective dearomative [3 + 2] annulation of 3-hydroxy chromanones with azonaphthalenes was realized using a chiral squaramide-tertiary amine as a catalyst. A large variety of chromanone fused indolines were obtained in moderate to good yields (up to 93%) with generally good enantioselectivities (up to 95% ee). The absolute configuration of one of the products was assigned by an X-ray crystal structural analysis, and a plausible reaction mechanism was proposed. Afterwards, two arylated derivatives were prepared by the Suzuki–Miyaura coupling of one of the products with aryl boronic acids.